The present invention is generally directed to toners, developers, and imaging processes, including a full color process for forming multiple color images, and more specifically, the present invention is directed to a process for obtaining multicolor, including two-color images which in an embodiment comprises charging an imaging member, creating on the member a latent image comprising areas of high, medium, and low potential, developing the low areas of potential with the magenta developer composition illustrated herein, subsequently developing the high areas of potential with a developer composition, transferring the developed image to a substrate, and optionally permanently affixing the image to the substrate. In embodiments, the toners and developers of the present invention can be utilized in specific color imaging processes, such as process color, and the like. An example of the aforementioned development process comprises a developer housing with a twin auger transport single magnetic brush design mounted in the approximate 6 o'clock orientation. The magnetic brush roll (developer roll) is about 30 millimeters in diameter, sandblasted for roughness, and preferably operates at about 1.5 times the speed of the photoreceptor, or imaging member. The developer roll is spaced about 0.5 millimeter from the photoreceptor and is biased with a square wave 550 volt RMS 2.0 KHz AC bias added to the DC bias which is variable between 0 and -500 volts depending upon the photoreceptor discharge characteristics, and the desired xerographic developability established by the control algorithm. A stationary magnet is situated internal to the rotating developer roll sleeve, and is comprised of a ferrite with a designed magnetic pole configuration to satisfy the requirements of controlling the developer transport and developability. The developer flow (termed Mass on the Sleeve, or MOS) can be controlled by the location of a low permeability trimmed bar in the magnetic field at the point of trimming. Typically, the MOS is set at 33.+-.3 mg/cm.sup.2 and is sensitive to the trim gap, toner concentration (TC) and developer tribo, hence, the developer housing has a toner concentration sensor as part of the process control circuitry. The twin augers in the developer housing sump transport the developer in opposite directions, first past the toner dispenser then to the developer pick up region of the developer roll. The augers have slits built into them in order to facilitate the mixing of the fresh toner added to the developer. Usually a number of latent images are formed and developed sequentially on the imaging member with an appropriate toner, such as that of the present invention for the magenta color. Another embodiment of the present invention relates to magenta toners comprised of toner resin particles, colored pigment particles, especially flushed FANAL PINK D4830.TM. (BASF), an optional negative charge enhancing additive, surface additives, such as colloidal silicas, like AEROSIL.RTM.#76, tin oxide, especially a tin oxide available as S-1; and polymeric hydroxy surface additives, such as UNILINS.RTM., reference U.S. Pat. No. 4,883,736, the disclosure of which is totally incorporated herein by reference. The toner in embodiments can be comprised of resin particles, a magenta pigment, preferably flushed into the toner resin, and surface additives of colloidal silica and UNILIN.RTM..
A number of advantages are associated with the toner of the present invention in embodiments thereof, including significantly improved color especially in the red and blue region, lower cost, lower fuser minimum fixing temperature (MFT), and improved fuser life. In another embodiment, there can be added to the toner a negative charge additive, such as an aluminum complex, as mentioned herein like BONTRON E-88.TM., available from Orient Chemical, thereby lowering the triboelectrical charge of the toner in embodiments; and the use of a common carrier for each colored toner. Also, there are provided in accordance with the present invention processes for obtaining passivated magenta toners, and more specifically wherein the magenta pigments are passivated thereby decreasing, or substantially eliminating their adverse effects on the electrical characteristics of the toner and developer compositions containing such pigments. Other advantages associated with the present invention include the provision of a developer with stable positive triboelectrical toner characteristics which enables the generation of high quality images subsequent to development, that is images with substantially no background deposits and substantially no smearing for a broad range of relative humidity conditions, that is for example from 20 to 80 percent relative humidity at an effective range of temperature zones ranging, for example, from about 20.degree. C. to about 80.degree. C.
Passivation can be achieved by, for example, the admixing of the magenta pigment and charge additives with the toner resin particles. One advantage associated with the processes of the present invention is the ability to generate high quality multicolor, especially three, images, one of which is magenta, and the other of which can be yellow and cyan in a single development pass.
Toner compositions with colored pigments are known. For example, there are disclosed in U.S. Pat. No. 4,948,686, the disclosure of which is totally incorporated herein by reference, processes for the formation of two color images with a colored developer comprised of a first toner comprised of certain resin particles, such as styrene butadiene, a first pigment such as copper phthalocyanine, a charge control additive, colloidal silica and metal salts of fatty acid as external surface additives, and a first carrier comprised of a steel core with, for example, a terpolymer overcoating; and a second developer comprised of a black toner, a second charge additive and a steel core carrier with certain polymeric overcoatings, see Claim 1 for example. Examples of colored toner pigments are illustrated in column 9, lines 10 to 26, and examples of charge additives for the toner are detailed in column 9, lines 27 to 43, of the aforementioned patent. For the black toner, there can be selected the components as recited in columns 10 and 11, including charge additives such as distearyl dimethyl ammonium methyl sulfate, see column 11, lines 16 to 32. Additionally, the working Examples of this patent detail the preparation of a number of specifc toners. Also, there is illustrated in U.S. Pat. No. 4,948,686 a process for forming two-color images which comprises, for example, (1) charging an imaging member in an imaging apparatus; (2) creating on the member a latent image comprising areas of high, intermediate, and low potential; (3) developing the low areas of potential by conductive magnetic brush development with a developer comprising a colored first toner comprising a first resin present in an amount of from about 80 to about 98.8 percent by weight and selected from the group consisting of polyesters, styrene-butadiene polymers, styrene-acrylate polymers, styrene-methacrylate polymers, and mixtures thereof; a first pigment present in an amount of from about 1 to about 15 percent by weight and selected from the group consisting of copper phthalocyanine pigments, quinacridone pigments, azo pigments, rhodamine pigments, and mixtures thereof; a charge control agent present in an amount of from about 0.2 to about 5 percent by weight; colloidal silica surface external additives present in an amount of from about 0.1 to about 2 percent by weight; and external additives comprising metal salts or metal salts of fatty acids present in an amount of from about 0.1 to about 2 percent by weight; and a first carrier comprising a steel core with an average diameter of from about 25 to about 215 microns and a coating selected from the group consisting of methyl terpolymer, polymethyl methacrylate, and a blend of from about 35 to about 65 percent by weight of polymethyl methacrylate and from about 35 to about 65 percent by weight of chlorotrifluoroethylene-vinyl chloride copolymer, wherein the coating contains from 0 to about 40 percent by weight of the coating of conductive particles and wherein the coating weight is from about 0.2 to about 3 percent by weight of the carrier; (4) subsequently developing the high areas of potential by conductive magnetic brush development with a developer comprising a black second toner comprising a second resin present in an amount of from about 80 to about 98.8 percent by weight and selected from the group consisting of polyesters, styrene-butadiene polymers, styrene-acrylate polymers, styrene-methacrylate polymers, and mixtures thereof; a second pigment present in an amount of from about 1 to about 15 percent by weight; and a second charge control additive present in an amount of from about 0.1 to about 6 percent by weight; and a second carrier comprising a steel core with an average diameter of from about 25 to about 215 microns and a coating selected from the group consisting of chlorotrifluoroethylene-vinyl chloride copolymer containing from 0 to about 40 percent by weight of conductive particles at a coating weight of from about 0.4 to about 1.5 percent by weight of the carrier; polyvinylfluoride at a coating weight of from about 0.01 to about 0.2 percent by weight of the carrier; and polyvinylchloride at a coating weight of from about 0.01 to about 0.2 percent by weight of the carrier; and (5) transferring the developed two-color image to a substrate. Imaging members suitable for use with the process of the copending application may be of any type capable of maintaining three distinct levels of potential. Generally, various dielectric or photoconductive insulating materials suitable for use in xerographic, ionographic, or other electrophotographic processes may be selected for the above process. Examples of suitable photoreceptor materials include amorphous silicon, layered organic materials as disclosed in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference, and the like.
Processes for obtaining electrophotographic, including xerographic, and two-colored images are known. In U.S. Pat. No. 4,264,185, the disclosure of which is totally incorporated herein by reference, there is illustrated an apparatus for forming two-color images by forming a bipolar electrostatic image of a two-color original document on a photoconductive drum. A first developing unit applies a toner of a first color and polarity to the drum and a second developing unit applies a toner of a second color and polarity to the drum to form a two-color electrostatic image which is transferred and fixed to a copy sheet. A bias voltage of the first polarity is applied to the second developing unit to repel the toner of the first color and prevent degradation of the first color toner image. A bias voltage of the second polarity is applied to the first developing unit to prevent contamination of the first color toner with the second color toner. Also, the following United States patents are mentioned: U.S. Pat. No. 4,308,821 wherein there is disclosed a method and apparatus for forming two-color images which employs two magnetic brushes; U.S. Pat. No. 4,378,415, which discloses a method of highlight color imaging which comprises providing a layered organic photoreceptor having a red sensitive layer and a short wavelength sensitive layer, subjecting the imaging member to negative charges, followed by subjecting the imaging member to positive charges, imagewise exposing the member, and developing with a colored developer composition comprising positively charged toner components, negatively changed toner components, and carrier particles; U.S. Pat. No. 4,430,402, which discloses a two-component type dry developer for use in dichromatic electrophotography which comprises two kinds of developers, each of which is comprised of a toner and a carrier, and wherein dichromatic images can be formed by developing a positively and negatively electrified electrostatic latent image successively with toners different in polarity and color from each other; U.S. Pat. No. 4,594,302 which discloses a developing process for two-colored electrophotography which comprises charging the surface of a photoreceptor with two photosensitive layers of different spectral sensitivities with one polarity, subsequently charging the photoreceptor with a different polarity, exposing a two-colored original to form electrostatic latent images having different polarities corresponding to the two-colored original, developing one latent image with a first color toner of one polarity, exposing the photoreceptor to eliminate electric charges with the same polarity as the first color toner which are induced on the surface of the photoreceptor in the vicinity of the latent image developed by the first color toner, and developing the other latent image with a second color toner charged with a polarity different from that of the first color toner; U.S. Pat. No. 4,500,616 which discloses a method of developing electrostatic latent images by selectively extracting colored grains of one polarity from a mixture containing colored grains having opposite polarity to each other in the presence of an alternating field, followed by development of the electrostatic image by the selectively extracted colored grains; U.S. Pat. No. 4,524,117 which discloses an electrophotographic method for forming two-colored images which comprises uniformly charging the surface of a photoreceptor having a conductive surface and a photoconductive layer sensitive to a first color formed on the conductive substance, followed by exposing a two-colored original to form on the photoconductive layer a latent image corresponding to a second color region in the original with the same polarity as the electric charges on the surface of the photoconductive layer; U.S. Pat. No. 4,525,447, which discloses an image forming method which comprises forming on a photosensitive member an electrostatic latent image having at least three different levels of potentials, or comprising first and second latent images and developing the first and second latent images with a three component developer; U.S. Pat. No. 4,539,281, which discloses a method of forming dichromatic copy images by forming an electrostatic latent image having a first image portion and a second image portion; U.S. Pat. No. 4,562,129, which illustrates a method of forming dichromatic copy images with a developer composed of a high-resistivity magnetic carrier and a nonmagnetic insulating toner, which are triboelectrically chargeable; U.S. Pat. No. 4,640,883, which discloses a method of forming composite or dichromatic images which comprises forming on an imaging member electrostatic latent images having at least three different potential levels, the first and second latent images being represented, respectively, by a first potential and a second potential relative to a common background potential; U.S. Pat. Nos. 4,045,218 and 4,572,651. The disclosure of each of the aforementioned United States patents are totally incorporated herein by reference.
The process of charging a photoresponsive imaging member to a single polarity and creating on it an image comprised of at least three different levels of potential of the same polarity is illustrated in U.S. Pat. No. 4,078,929, the disclosure of which is totally incorporated herein by reference. This patent discloses a method of creating two-colored images by forming on an imaging surface a charge pattern including an area of first charge as a background area, a second area of greater voltage than the first area, and a third area of lesser voltage than the first area with the second and third areas functioning as image areas. The charge pattern is developed in a first step with positively charged toner particles of a first color and, in a subsequent development step, developed with negatively charged toner particles of a second color. Alternatively, charge patterns may be developed with a dry developer containing toners of two different colors in a single development step. Also of interest with respect to the trilevel process for generating images is U.S. Pat. No. 4,686,163, the disclosure of which is totally incorporated herein by reference.
The photoresponsive imaging member can be negatively charged, positively charged, or both, and the latent image formed on the surface may be comprised of either a positive or a negative potential, or both. In one embodiment, the image comprises three distinct levels of potential, all being of the same polarity. The levels of potential should be well differentiated, such that they are separated by at least 100 volts, and preferably 200 volts or more. For example, a latent image on an imaging member can comprise areas of potential at -800, -400, and -100 volts. In addition, the levels of potential may comprise ranges of potential. For example, a latent image may consist of a high level of potential ranging from about -500 to about -800 volts, an intermediate level of potential of about -400 volts, and a low level ranging from about -100 to about -300 volts. An image having levels of potential that range over a broad area may be created such that gray areas of one color are developed in the high range and gray areas of another color are developed in the low range with 100 volts of potential separating the high and low ranges and constituting the intermediate, undeveloped range. In this situation, from 0 to about 100 volts may separate the high level of potential from the intermediate level of potential, and from 0 to about 100 volts may separate the intermediate level of potential from the low level of potential. When a layered organic photoreceptor is employed, preferred potential ranges are from about -700 to about -850 volts for the high level of potential, from about -350 to about -450 volts for the intermediate level of potential, and from about -100 to about -180 volts for the low level of potential. These values will differ depending upon the type of imaging member selected.
Moreover, illustrated in copending application U.S. Ser. No. 500,335/91, the disclosure of which is totally incorporated herein by reference, are developers, toners and imaging processes thereof. In an embodiment of the copending application, there is provided a process for forming two-color images which comprises (1) charging an imaging member in an imaging apparatus; (2) creating on the member a latent image comprising areas of high, intermediate, and low potential; (3) developing the low areas of potential by, for example, conductive magnetic brush development with a developer comprising carrier particles, and a colored first toner comprised of resin particles, colored, other than black, pigment particles, and an aluminum complex charge enhancing additive; (4) subsequently developing the high areas of potential by conductive magnetic brush development with a developer comprising a second black developer comprised of carrier particles and a toner comprised of resin, black pigment, such as carbon black, and a charge enhancing additive; (5) transferring the developed two-color image to a suitable substrate; and (6) fixing the image thereto. In an embodiment of the aforementioned copending application the first developer comprises, for example, a first toner comprised of resin present in an effective amount of from, for example, about 70 to about 98 percent by weight, which resin can be selected from the group consisting of polyesters, styrene-butadiene polymers, styrene-acrylate polymers, styrene-methacrylate polymers, Pliolites.RTM., crosslinked styrene acrylates, crosslinked styrene methacrylates, and the like wherein the crosslinking component is, for example, divinyl benzene, and mixtures thereof; a first colored blue, especially PV Fast Blue.TM. pigment present in an effective amount of from, for example, about 1 to about 15 percent by weight, and preferably from about 1 to about 3 weight percent; an aluminum complex charge enhancing additive; and a second developer comprised of a second toner comprised of resin present in an effective amount of from, for example, about 70 to about 98 percent by weight, which resin can be selected from the group consisting of polyesters, styrene-butadiene polymers, styrene-acrylate polymers, styrene-methacrylate polymers, Pliolites.RTM., crosslinked styrene acrylates, crosslinked styrene methacrylates, and the like wherein the crosslinking component is, for example, divinyl benzene, and mixtures thereof; and a black pigment present in an effective amount of from, for example, about 1 to about 15 percent by weight, and preferably from about 1 to about 5 weight percent wherein the aforementioned black toner contains a charge enhancing additive such as an alkyl pyridinium halide, and preferably cetyl pyridinium chloride, and in a preferred embodiment the black toner is comprised of 92 percent by weight of a styrene n-butyl methyacrylate copolymer (58/42), 6 percent by weight of Regal 330.RTM. carbon black, and 2 percent by weight of the charge enhancing additive cetyl pyridinium chloride.
Illustrated in copending application U.S. Ser. No. 547,362/91, the disclosure of which is totally incorporated herein by reference, is a process for forming two-color images which comprises (1) charging an imaging member in an imaging apparatus; (2) creating on the member a latent image comprising areas of high, intermediate, and low potential; (3) developing the low areas of potential by, for example, conductive magnetic brush development with a developer comprising carrier particles, and a colored first toner comprised of resin, a positively charging pigment, and a negatively charging pigment; (4) subsequently developing the high areas of potential by conductive magnetic brush development with a developer comprising a second developer comprised of carrier particles and a toner comprised of resin, black pigment, such as carbon black, and a charge enhancing additive; (5) transferring the developed two-color image to a suitable substrate; and (6) fixing the image thereto.